1. Field of the Invention
The invention relates in general to a motherboard, and more particularly to a motherboard having an expandable PCI Express slot.
2. Description of the Related Art
Computer bus specifications have been developed from the ISA architecture (16 bit@8.33 Mhz) of the 1980 years to the Peripheral Component Interconnect (PCI) architecture (32 bit@33 Mhz) of the 1990 years and to the current AGP architecture (32 bit@66 Mhz). In the current peripheral interface card, particularly the graphics card (or display card), however, the data transmission amount thereof is getting more and more insufficient under the transmission architecture of the bus AGP. So, a new Peripheral Component Interconnect Express (PCI Express) bus specification has been proposed.
The PCI Express utilizes the switch type peer-to-peer sequence transmission technology. The data transmission of the PCI Express utilizes a transmitter (Tx) and a receiver (Rx), which constitute a simplex lane. Each PCI Express individually utilizes its own lane to communicate with the corresponding chipset on the motherboard, and the bus-sharing architecture of the conventional PCI is no longer used.
The current transmission speed in the PCI Express single lane may reach 250 MB/s, and the occasion in the single lane is referred to as the PCI Express x1 (one lane) having a transmission bandwidth of 1×500=500 MB/s. In order to cover the transmission bandwidth requirements in various level fields, the current PCI Express has various specifications of x1, x2, x4, x8, x16, x32, and the like. Different specifications have different lead size, and thus have different physical lengths and lanes numbers. The transmission bandwidth between the motherboard chipset and the graphics interface starts from the PCI Express x16 specification to 8 GB/s, which is sixteen times that of the PCI Express x1 and approaches four times of the current AGP X8 of 2.1 GB/s.
FIG. 1 (prior art) is a schematic illustration showing a conventional motherboard. Referring to FIG. 1, the conventional motherboard 100 generally includes a PCI Express x16 slot 110, two PCI Express x1 slots 120 and 130, and a chipset (not shown in FIG. 1). The PCI Express x16 slot 110 is able to accept the PCI Express x1, x2, x4, x8 and x16 interface cards, but the PCI Express x1 slot is able to accept only the PCI Express x1 interface card.
However, the display card or graphics card available in the commercial market would be the specification of PCI Express x16 and includes only one PCI Express slot (i.e. the PCI Express x16 slot 110 of FIG. 1) on the conventional motherboard 100 to accept the PCI Express x16 interface card. Thus, the conventional motherboard 100 can't drive the extend monitor that needs another PCI Express x16 display card to support, even if the PCI Express x1 slots 120 and 130 disposed on the motherboard.